摘要:

SUMMARYThe images of complex biological structures seen in the electron microscope, possessing ann‐fold rotational symmetry, can be enhanced by averaging the axially repeating motif in order to improve their signal‐to‐noise ratio; this requires that the slices withn‐fold symmetry do not exhibit distortions relative to one another.A strategy is proposed to detect the relative distortions and to remove them in order to obtain reliable results from the averaging process. Extensive use is made of cross‐correlation analysis and of interpolation; because the procedure involves iterated resampling of the image, it is essential to adopt interpolation algorithms which preserve the spectral power.The procedure is illustrated by the analysis of transverse sections of the sperm flagellum axoneme of a stick insect; it might be used for the reconstruction of microtubules, nuclear pore complexes, virus capsids, and other supramolecular aggregates. The reconstructed images of axoneme sections reveal new information about the interactions between adjacent doublets; in particular, a double conjunction connecting the inner dynein arm with the nearest B‐tubule has been consistent

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03186.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYWe present a simple theory for the evaluation of the axial resolution of a confocal scanning microscope with parallel‐beam detection. The results demonstrate that, in certain cases, the collection efficiency is low compared with a conventional confocal microscope, but the axial resolution may be further improve

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03187.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYIt is shown that for a variety of biological particle shapes, the volume‐weighted second moment of particle volume can be estimated stereologically using only the areas of particle transects, which can be estimated manually by point‐count

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03188.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYA combination of cryofixation without pre‐treatment, freeze‐substitution and low‐temperature embedding was used to prepare specimens ofPenicillium chrysogenumfor electron microscopy. To produce specimens which are thin enough for appropriate cryofixation, theP. chrysogenumcolonies were grown between dissected‐dialysis tubing on an agar plate, which in addition allowed longitudinal sectioning. In contrast to classical chemical fixation, this preparation procedure resulted in excellent preservation of ultrastructure. Furthermore, the penicillin biosynthetic enzyme acyltransferase could be unequivocally located by immunogold labelling, indicating a preservation of antigenic properties of the specimen. Labelling density was not conspicuously affected when using different freeze‐substitution media, but it was reduced after embedding in

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03189.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYA method is described using a microwave oven and acidified 2,2‐dimethoxypropane to fix and dehydrate nematode tissue rapidly in preparation for transmission electron microscopy. Nematode tissue prepared using this method is well preserved compared with tissue fixed by conventional methods. The technique also enabled fixation of unhatched nematodes in the egg, a process that is almost impossible to achieve using conventional methods of fixation. Using the method described, differences were found between the cuticles of different nematode stage

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03190.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYImmunofluorescence staining techniques at present, when applied to follow the expression of HIV‐1‐specific antigens on infected cells, only give the information that the antigens detected are localized in the outer region of the membrane of the infected cell. We therefore set up a procedure using magnetic polystyrol particles coated with antibodies specific for the HIV‐1 antigens under study, in combination with scanning electron microscopy. We were able to demonstrate that p24 and p18 structural antigens are clearly expressed on the surface of HIV‐1‐infected H9 lymphocytes. This means that there was no steric hindrance for structures of cell‐like size specific for HIV‐1 antigens to interact with their target antigens. Other antigens may be hidden in membrane structures and are therefore inaccessible, for example, to the beads used here, which were of a similar size to antigen‐specific cellsin vivo. The results of this model system must be seen with respect to the interaction of antigen‐specific cell‐mediated immunity with full antibody‐dependent cellular cytotoxicity, or without cytotoxic T lymphocytes, the mediator f

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03191.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYA method which enables visualization of the position of the focused ultraviolet (UV) light (260–300 nm) in a UV microbeam apparatus is described. The UV light is focused onto uranyl acetate which fluoresces. The fluorescence is of low intensity, but can be visualized using a TV‐camera sensitive to low light levels. This is a simple, quick, and objective way to locate the position of the focused UV light in UV microb

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03192.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYWhen a microregion in a thin section of frozen‐dried and embedded tissue is analysed by the conventional electron‐probe X‐ray continuum‐normalization method, the measured quantity is in mmol of element per kg of embedded specimen. As each microregion contains an unknown amount of embedding medium, this quantity generally lies indeterminately somewhere within the wide range between mmol of element per kg of hydrated tissue and mmol of element per kg of dehydrated tissue. However, if a ‘tag’ element is incorporated in the embedding medium, the contribution of the medium to the local continuum count in each probed field should be measurable, and the X‐ray data may then unambiguously yield mmol of element per kg of dehydrated tissue. This result should not be affected by shrinkage on freeze‐drying or by incomplete replacement of water by embedding medium.The same X‐ray data can additionally provide estimates of mmol of element per unit volume, mmol of element per kg of hydrated tissue and local dry‐mass fraction. However, these estimates are subject to errors due to tissue shrinkage, incomplete replacement of wa

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03193.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYThe particle size distribution of polymer latexes of, for example, polybutadiene can be measured on transmission electron micrographs using image analysis methods. By taking suitable measures in preparing the sample it can be ensured that the image only consists of projections of two‐dimensional clusters of adhering latex spheres. For the deagglomeration of these clusters a number of methods based on mathematical morphology are discussed. Speed and accuracy of the methods were tested on a personal‐computer‐based image analysis system and compared to manual measurements.Repeated openings or erosions applied to a binary image are relatively fast global methods with a low accuracy due to the fact that particle diameters are measured in whole numbers of pixels; only the horizontal diameters of rectangular pixels are measured.With an iterative method the individual components of the clusters are found by repeated conditional thickening of the erosion kernels. The method is accurate but very slow due to the large number of processing steps.The watershed method as applied to the original grey‐scale transmission electron micrograph makes use of the sharp local maxima which arise at the interface of the projection of two adhering particles. This method is as accurate as the iterative method, but about eight times

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03194.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYTime relation curves are given for Formvar membrane contraction or collodion membrane dilation under electron‐beam irradiation. Also, numerical values are given for the contraction or dilation measured in different zones of the Formvar or collodion support membrane

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03195.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY